Concrete slabs may be formed in various ways. Wooden boards have long been used in forming sidewalks, driveways, and footings for dwellings, for example. Deformation of wood due to heat and moisture, and the ever-increasing need for greater precision in dimensioning and leveling concrete slabs has, however, escalated the use of metal forms. Apart from being more dimensionally stable and controllable, metal forms may be manufactured with channels which allow one slab to feature a "key" that projects into the formed channel in an adjacent slab. Such joints are known as keyed joints, and are important in limiting movement of adjacent slabs with respect to each other.
Various techniques have been employed for connecting metal joint forms to the stakes which fasten the forms to the ground or other underlying substrate. U.S. Pat. No. 4,455,104 to Weisbach, for example, discloses a form whose top edge and cross section is folded over to form a downturned flange that has its lower edge hemmed on the inside to capture vertical rows of serrations on metal stakes which fasten the form to the substrate. U.S. Pat. No. 3,784,313 to Collier also features a form with folded over upper edge that captures protrusions on stakes.
Other designs exist which assist in retaining the form on the stakes. For instance, U.S. Pat. No. 3,561,721 to Self shows a joint form that includes periodic openings which receive ears that have been formed in the upper portions of the stakes by punching or cutting and bending. Barb members on such ears assist in helping retain the form on the stakes. These three patents by Weisbach, Collier, and Self are incorporated herein by this reference.